It is known that the lid of each element of a lead-acid accumulator must perform two main and essential functions. The first function is that of granting tightness, so as to avoid possible leaks of the electrolyte contained within the accumulator, thereby preventing damage which could be caused by said electrolyte because of its high corrosive power.
The second function is that of allowing the lengthening of the positive pole, which will become longer during the life span of the accumulator due to a known electrochemical phenomena. The lengthening of the pole must occur so that it does not exert any pressure against the lid to which it is attached, so as not to cause the rupture or the disconnection of the lid itself. Since the lengthening of the positive pole, due to the aging process is between 0,5 and 2%, the phenomenon acquires a special relevance in industrial accumulators where the elements reach heights sometimes exceeding 650 mm.
A known solution of this problem consists in sealing the area between the lid and the accumulator case with a plastic-type binder which insures the tightness between the lid and the case and, at the same time, a certain, although limited, elasticity. This expedient solves the problem in car accumulator batteries, but it does not solve the problem in the industrial accumulators, which, as has been said, are very tall.
In view of solving the problem of the lengthening of the positive pole in very tall accumulators, lids have been developed, which in the pole connection area, have a special shape and a decrease in the lid thickness in order to make the lid elastically deformable in correspondence with the poles. This expedient, which solves the problem of the lengthening of the positive pole presents, however, the disadvantage that, in order to apply it in the manufacture of lids for accumulators having a width which is much reduced in relation to its height, as in the case of lids for 2PzS-type accumulators according to the DIN 43595 standards, it is necessary to drastically reduce the diameter of the poles.
In fact, because of the limited width of the lid, in order to have available on the lid the space which is indispensable for obtaining a special shape and the thickness reduction in correspondence with the poles, the only possibility is in fact that of decreasing the diameter of the poles.
The disadvantages arising from a decreased diameter in the poles are obvious.
A first disadvantage originates from the increased current density passing through the pole in this case, which generates more heat with a subsequent energy loss.
Another disadvantage consists in the necessity of having to use, for the 2PzS-type accumulators according to DIN Standards, poles having a smaller diameter than the poles which are normally used in the manufacture of the 3PzS accumulators and of the subsequent sizes, with the ensuing economical and organizational difficulties due to the necessity of having to maintain a stock of poles of two different sizes.
Pat. No. 85653/A/81 has been registered in the name of the inventor of the present invention, in which there has been described a lid for accumulators presenting a special concave shape suited to guarantee the elasticity and the lengthening of the poles, even in the case of lids having a limited width in relation to their length and overcoming the above-mentioned disadvantages.
Although this type of lid overcomes the lamented disadvantages, it still presents a limited elasticity when its width is considerably reduced in relation to its length, as is the case of the 2PzS-type lids according to the DIN 43595 Standards.
The purpose of the present invention is that of overcoming even this last limitation.
The main object of the present invention is that of providing a lid for lead-acid accumulators presenting elastic and deformable pole seats.
Another object of the present invention is that of obtaining a lid allowing the deformation of the accumulator poles, the elasticity of the seats connecting the poles with the lid being independent from the dimensions of the lid and constant under any circumstance.
Yet another object of the present invention is that of obtaining a lid for accumulators which allows the assembly of poles which are also assembled on the 3PzS-type lids, without impairing the elasticity of the lid.
Another object of the present invention is that of obtaining a lid for accumulators the usable width of which can, in any case, be totally used for the lodging of the poles.
A further object of the present invention is that of obtaining a lid for accumulators with removable poles which can be connected to the lid by means of a threaded bushing, so as to make it possible and easy to take them apart to facilitate their maintenance.
The above mentioned objects and others, which will be better set forth hereinbelow are fulfilled by the construction of a lid for lead-acid accumulators, which, in accordance with the claims, is characterized in that the seats for the connection of the poles present a diaphragm with a circular cross-section, which is elastic and flexible in its axial direction and is arranged coaxially around each opening for the passage of the accumulator poles, said diaphragm being connected on one side with the lid surface, while its opposite end presents a ring-shaped seat with an inner shoulder having an indented diameter and being suited to receive and hold in place the bushing locking the accumulator pole.
The obvious advantages of the present invention reside in the fact that the diaphragm permits the axial sliding of the pole in relation to the lid, while said diaphragm does not take up any significant space around the pole itself. It follows that the elasticity of the lid, which is meant to allow the sliding of the pole in relationship to the lid, is insured even in those accumulator batteries wherein the width of the lids only slightly exceeds the diameter of the poles and, for this reason, can not accept a completely flexible and elastic ring-shaped area around the pole.